The present invention relates to a mobile switching apparatus for use in a pool of mobile switching apparatuses provided for a mobile cellular communication network, a pool of mobile switching apparatuses, a router apparatus for operation between at least one access network control apparatus and a pool of mobile switching apparatuses and related methods.
Basic subsystems for the architecture of mobile cellular communication systems are a core network and a radio access network.
As shown in FIG. 11, the core network comprises a gateway switching center GMSC, a mobile switching center MSC, further a home location register HLR, and a visitor location register VLR. The gateway switching center GMSC is connected to a plurality of mobile switching centers MSC and each mobile switching center MSC is connected to a visitor location register VLR. Different visitor location registers VLR are connected to the home location register HLR which is also linked to the gateway switching center GMSC.
As also shown in FIG. 11, each mobile switching center MSC serves a plurality of base station controllers BSC being itself connected to a plurality of base transceiver stations BTS for link establishment to mobile stations MS roaming in the area covered by the mobile cellular communication network.
The architecture of a mobile cellular communication network allows interworking between a fixed network such as a public switched telephone network PSTN like a national telephone network, an integrated services digital network ISDN, a public switched data network PSPDN and/or a public land mobile network PLMN like a global system for mobile communications GSM, a digital cellular system DCS 1800, a personal communication system PCS, and/or a third generation 3GPP mobile communication system.
Operatively, the home location register HLR stores two types of information, i.e. subscriber information and mobile information to allow incoming calls to be routed to a mobile station MS. Further, the visitor location register VLR is a functional unit that dynamically stores mobile station information, e.g., location area in case a mobile station is located in an area covered by the visitor location register VLR, and also subscriber profiles for visiting subscribers.
Further, the mobile switching center MSC performs necessary switching functions required for mobile stations MS covered by the mobile service switching center MSC. Also, the mobile switching center MSC monitors the mobility of its mobile stations MS and manages the necessary resources required to handle and update location registration procedures.
Besides the components of the core network of a mobile cellular communication network discussed so far, also components necessary to achieve a radio access to the mobile station must be provided in an access network. The access network comprises a plurality of, e.g., base station subsystems BSS for 2nd generation mobile communication systems or radio network controllers RNC for 3rd generation mobile communication systems. These subsystems correspond to physical equipment providing radio coverage to prescribed geographical areas known as cells illustrated as hexagonal geographical regions in FIG. 11. Each base station subsystem BSS contains equipment required to communicate with the mobile station MS.
Operatively, a base station subsystem BSS provides a control function implemented in a base station controller BSC/a radio network controller RNC and a transmitting function performed by a base station transceiver system BTS. The base station transceiver system BTS corresponds to a radio transmission equipment and covers each cell. A base station subsystem BSS can serve several cells because it may comprise multiple base transceiver systems BTS.
In mobile communication systems of the type outlined above the control of communication processes is achieved through signaling messages between control instances. Signaling messages are transferred both downlink to the mobile station for mobile terminating control signaling and uplink for mobile originating control signaling.
An example for mobile terminating control signaling in a mobile cellular mobile communication networks is the establishment of mobile terminating calls. This mobile terminating control signaling may be separated into two different phases. During establishment of a mobile terminating call the first phase consists of the following steps:
analysis of the called number (B-number) in the gateway switching center GMSC;
interrogation of the home location register HLR;
provision of a roaming number MSRN/TLDN through the visitor location register VLR;
routing of the call from the gateway switching center to the visited VMSC;
sending a paging request to an access node of the access network for further submission by the access nodexe2x80x94e.g., a base station controller BSC or a radio network controller RNCxe2x80x94to the mobile terminal, e.g., by broadcasting.
Further, the second phase of a mobile terminating call establishment comprises the steps:
receiving a paging response from the called mobile station; and
processing of the paging response and completion of the call setup.
It should be noted that between the mobile switching center MSC and the activated base station controller BSC handling the paging these two phases are treated as completely independent signaling transactions. Therefore, these different signaling transactions must be linked in the mobile switching center MSC. Within existing mobile communication networks this can be done, as the paging request is initiated by the same mobile switching center MSC that also receives the related paging response from the activated base station controllers. In other words, the two phases outlined above may be linked since each base station controller BSC is served by a single mobile switching center MSC only.
However, this simple mechanism will not work in case the 1:n relationship between a mobile switching center MSC and related base station controllers BSC is generalized to a case where each base station controller may be served by a plurality of mobile station centers MSC to increase network capacity and reliability.
In other words, when the base station controller BSC may initiate paging responses to mobile switching centers MSC different from the mobile switching center issuing the related paging request, the link between the two phases of mobile terminating call establishment outlined above cannot be achieved using the existing mechanisms as the mobile switching center MSC receiving a paging response may differ from the mobile switching center MSC initiating a related paging request.
Nevertheless, this might be a pre-requisite to meet future service demands since for large mobile cellular communication networks a static link between access nodes and mobile switching centers MSC could turn out to be an inefficient way of using the core network. When subscribers concentrate in one areaxe2x80x94e.g., urban areas during business hoursxe2x80x94or during disasters hitting only a certain area of the mobile communication network, the occasion would occur that a lot of calls overload a specific mobile switching center MSC while other mobile switching centers MSC in the mobile cellular communication network still have excess capacity to handle calls.
The problems become even more difficult when mobile communication networks cover very large areas, e.g., spanning more than one time zone. There exists no possibility to do load sharing over available mobile switching centers MSC to spread high load during peak hours in different time zones, e.g., between Dallas and Los Angeles.
Similar problems as outline above with respect to mobile terminal terminating signaling traffic also exist with respect to mobile terminal originating signaling traffic when access nodes have the choice to access different mobile switching centers MSC.
For BSS (TR 23.913 v 1.0.0) there is described a subscriber based mechanism for load distribution for 3rd generation mobile cellular communication systems. Mobile station originating signaling messages are distributed to different mobile switching centers MSC on the basis of the subscriber identity comprised in a signaling message. However, this approach requires the analysis of signaling messages to find subscriber identities and therefore introduces delays as possible bottlenecks.
Referring only to subscriber identities could decrease the scope of flexibility. Further, when a mobile switching center is out of order related subscribers cannot receive signaling messages.
In view of the above, a first object of the present invention is to achieve an efficient relay of paging response messages to related paging requests in a core network with pooled mobile switching centers.
A second object of the present invention is to achieve an efficient and flexible routing of signaling messages between a core network and an access network.
According to the present invention, this object is achieved through a mobile switching apparatus for use in a pool of mobile switching apparatuses provided for a cellular communication network, comprising a signaling unit adapted to issue a paging message to an access network BSS/RNC served by the mobile switching apparatus for connection establishment to a mobile terminal MS, a relay unit adapted to receive a paging response from the access network BSS/RNC and to determine a mobile switching apparatus in the pool of mobile switching apparatuses handling the paging response, and a pool interface unit adapted to an exchange of information to at least one further mobile switching apparatus in the pool of mobile switching apparatuses.
Therefore, according to the present it is proposed to provide mobile switching apparatuses supporting a pool concept and having the capability of relaying a paging request issued by a mobile switching apparatus of the pool and a paging response received by a mobile switching apparatus of the pool.
The mobile switching apparatus according to the present invention is of particular use when service capabilities in existing mobile switching networks are extended, e.g., in highly congested rural areas, and/or to comply with an increasing number of subscribers in such mobile cellular communication networks. A particular advantage of the inventive mobile switching apparatus is thatxe2x80x94as long as the frequency allocation for the different cells remains unchangedxe2x80x94the service capability of cellular mobile communication networks may be extended only by installation of a mobile switching server pool and providing an access to an existing access network or by extending an already existing mobile switching apparatus pool with additional mobile switching apparatuses according to the present invention. This concept requires only a very low administrative overhead in that the mobile switching apparatus pool has only a minimum impact on existing mobile communication infrastructure.
Further, the present invention allows to extend processing capacity in a mobile communication network by adding, e.g., mobile switching apparatuses to the pool having dedicated service capability, e.g., voice and/or data. Important to note that such an extension of services may be implemented without service interrupt and therefore without loss of revenues for the network operator.
Further, the integration of a plurality of mobile switching apparatuses according to the present invention into a pool allows to increase the area that may be reached through globing paging, i.e. the area reachable through all mobile switching apparatuses in the pool.
Yet another advantage of the mobile switching apparatus according to the present invention is that data necessary for the operation of each single mobile switching apparatus may be stored and updated at only single locations so that the administrative overhead for the operator to maintain correct data for the operation of each mobile switching apparatus in the poolxe2x80x94e.g., radio configuration dataxe2x80x94is minimized.
In conclusion, the mobile switching apparatus according to the present invention allows to introduce a mechanism to spread signaling related functions over the pool of mobile switching apparatuses in a distributed architecture without the requirement to share the knowledge about the distributed architecture with the access network. It is possible to assign specific subscribers or services to a specific mobile switching apparatus in the pool. Also, the inventive concept is compatible with existing standards, e.g., second and future third generation cellular mobile communication networks.
According to a preferred embodiment of the inventive mobile switching apparatus, the relay unit comprises a mobile terminal identification unit adapted to evaluate whether a mobile subscriber issuing a paging response is known locally in the mobile switching apparatus.
This preferred embodiment of the invention allows to identify a situation where a mobile switching apparatus in the pool issuing a paging message to the access network is different from a mobile switching apparatus in the pool receiving a related paging response. In other words, this preferred embodiment forms the basis to realize the mobile switching apparatus pooling concept also for connectionless signaling processes.
According to another preferred embodiment of the present invention the relay unit comprises a retrieval unit adapted to identify the mobile switching apparatus in the pool issuing a paging message when the mobile subscriber issuing a related paging response is not known locally in the receiving mobile switching apparatus. Preferably, the receiving mobile switching apparatus in the pool may then submit the received paging response to the mobile switching apparatus issuing the paging message to the access network.
This preferred embodiment of the present invention provides a loop back mechanism for finalizing a paging process in the mobile switching apparatus in the pool that originally issued a paging message to the access network. This approach is highly efficient in that the data necessary for the handling of the paging responsexe2x80x94e.g., the profile of a user requesting a mobile station terminating callxe2x80x94are known locally at the mobile switching apparatus issuing the paging message. In conclusion, the overall request for data transfer within the pool of mobile switching apparatuses and therefore the time required for processing the paging response is minimized.
The same advantage applies when the signaling unit is adapted to handle the paging response locally when the mobile subscriber issuing the paging response is known locally in the switching apparatus, e.g., when the paging response is received by the mobile switching apparatus that also issued the related paging message.
According to yet another preferred embodiment of the present invention the relay unit further comprises a selection unit adapted to specify a mobile switching apparatus in the pool handling the paging response according to a specified selection algorithm.
This preferred embodiment of the present invention allows to freely specify a mobile switching apparatus in the pool for processing of the paging response, irrespective of which mobile switching apparatus in the pool issued a paging message or which mobile switching apparatus in the pool received the related paging response. A particular advantage is that such an approach allows for free configuration of the mobile switching apparatus pool such that, e.g., dedicated mobile switching apparatuses are provided for specific services, user groups, and/or a combination thereof. Further, this preferred embodiment allows a dynamic spreading of offered signaling traffic over available mobile switching apparatus capacity in the pool in view of a dynamic change of available resources in each mobile switching apparatus of the pool.
According to yet another preferred embodiment of the present invention, the relay unit in the mobile switching apparatus comprises a paging response modification unit adapted to change a called address in the paging response to an address of the paging message originating mobile switching apparatus or to an address of the selected mobile switching apparatus. Preferably, the paging response modification unit is further adapted to notify a core network about a paging message modification.
This preferred embodiment of the present invention allows to always achieve consistency of data both in the core network and in the access network of the cellular mobile communication network. As long as the calling addressxe2x80x94i.e. the address of the mobile equipment used by the subscriberxe2x80x94remains unchanged, always a consistent signaling between the core network and the access network is guaranteed. Even when the subscriber is moving (handover) signaling will still be consistent.
Further, to the advantages outlined above with respect to the inventive mobile switching apparatus it should be noted that the same principles may be used to relay a connection request within a single mobile switching apparatus internally in the case the handling of paging responses is distributed over multiple processors in a single mobile switching apparatus, e.g., using distributed memory.
Yet another advantageous application scenario for the mobile switching apparatus according to the present invention is global paging. Here, one solution within the framework of the present invention is to send a paging response to any mobile switching apparatus in the pool. The mobile switching apparatus may then inform all mobile switching apparatuses in the pool about the received mobile subscriber identity so that the one mobile switching apparatus that initiated the global paging message may, e.g., respond to the receiving mobile switching apparatus with its mobile switching identity for relaying the response to a global paging message thereto.
Yet another solution is that the paging response is sent to all mobile switching apparatuses in the pool. Each mobile switching apparatus will check whether the mobile subscriber is known locally. Then, the one mobile switching apparatus where the mobile subscriber is known locally will continue the processing of the paging response. The rest of the mobile switching apparatuses in the mobile will discard the paging response.
A second aspect of the present invention relays to a pool of mobile switching apparatuses operated in a cellular communication network. The pool comprises at least two mobile switching apparatuses as described above, a pool controller adapted to select a mobile switching apparatus in the pool for issuing a paging message to an access network served by the pool. The paging message serves to establish a connection to a mobile terminal. Further, the pool comprises a pool data base adapted to store the paging message in relation to the selective paging message issuing mobile switching apparatus in the pool. The stored relation may then be provided to any mobile switching apparatus in the pool on request.
This aspect of the present invention allows to achieve high data consistency in a very efficient manner in that all mobile switching apparatuses of the pool have access to the same pool data base. Further, the administrative effort for the network operator is minimized as only a single data base has to be supplied with data and subsequently be updated. Yet another advantage of the provision of a single pool data base is that the relation between an issued paging method and a received paging response may be resolved within a minimum time period. This particularly is the case when the pool data base also supplies information for call setup to a mobile switching apparatus in the pool handling a paging response from the access network.
According to a preferred embodiment of the pool of mobile switching apparatuses the pool controller is connected to a capability data base storing service capabilities of at least one mobile switching apparatus in the pool and/or the service availability of at least one mobile switching apparatus in the pool.
The provision of a capability data base allows for an efficient load sharing mechanism between the mobile switching apparatuses in the pool. Additionally, mobile equipment terminating calls may be grouped according to related service profiles to specific mobile switching apparatuses in the pool in compliance with the data stored in the capability data base. In addition, it may be possible to indicate shutdown of a specific mobile switching apparatus to avoid any loss of signaling traffic running over the pool of mobile switching apparatuses and therefore also to avoid any loss of revenue for the network operator.
According to yet another preferred embodiment of the inventive pool of mobile switching apparatuses, the pool controller is adapted to select a mobile switching apparatus in the pool randomly, in a predefined order, according to a service capability and/or according to a service availability profile stored in the capability data base.
According to this preferred embodiment, the operation of the pool controller may be configured according to different requirements, e.g., maximum load sharing in the pool of mobile switching apparatuses, avoidance of signaling traffic interruption, etc., while the pool of mobile switching apparatuses behaves to the outside world as one mobile switching apparatus.
While in the above specific embodiments of the mobile switching apparatus according to the present invention and the integration of a plurality of such mobile switching apparatuses into a pool have been described, in the following a third aspect of the present invention being related to the interfacing between the call network and the access network will be referred to.
In particular, the third aspect of the present invention relates to a router apparatus for operation between at least one access network control apparatus and a pool of mobile switching apparatuses as outlined above.
According to the present invention, the router apparatus comprises a pool interface unit connecting the router apparatus to each mobile switching apparatus in the pool and further an access network interface unit adapted to connect the router apparatus to the at least one access network controller apparatus. A selection unit is provided to select a mobile switching apparatus in the pool for connection to an access network controller apparatus for at least one signaling connection. The relation between the mobile switching apparatus in the pool, the related access network controller apparatus and the signaling connection can be stored in a storage unit. To handle a plurality of signaling connections, there is provided a bridging unit between the pool interface unit and the access network interface unit to selectively connect one access network control apparatus with one pooled mobile switching apparatus in accordance with signaling related information stored in the storage unit. For connectionless signaling messages no storage of information is necessary.
Therefore, the router according to the present invention enables stand alone dynamic routing of signaling messages. The router may be used to connect either second generation access nodes like BSCs or third generation access nodes like RNCs without impact on the functionality of the access node. Further, the router may support the exchange of both connection oriented messages and connectionless messages, e.g., on a signaling connection control part SCCP user level.
A further advantage of the inventive router apparatus is that it is freely configurable to be connected to a plurality of mobile switching apparatuses and also to a plurality of access nodes. Alternatively, the router apparatus may be connected to a plurality of mobile switching apparatuses and to only a single access node. Yet another alternative would be to, integrate the router apparatus into a single access node BSC, e.g., into a base station controller BSC or a radio network controller RNC. All alternatives achieve a transparent link between the mobile switching apparatus pool and the group of access nodes such that from the access node point of view the router apparatus acts like a mobile switching apparatus (with the exception that signaling messagesxe2x80x94e.g. connectionless signaling messagesxe2x80x94may be altered) and from the mobile switching apparatus point of view the router apparatus acts like an access node meaning that there exists no impact on the core network and access network architecture.
According to another preferred embodiment of the present invention there are provided computer program products directly loadable into the internal memory of processors running in a pooled mobile switching apparatus or controller, e.g., a pool controller, a router apparatus and access network controllers BSC/RNC, and comprising software code portions for performing the method steps according to the present invention when the product is run on the processor.
Therefore, the present invention is also provided to achieve an implementation of the inventive method steps on computer or processor systems. In conclusion, such implementation leads to the provision of computer program products for use with a computer system.
These programs defining the functions of the present invention can be delivered to a computer/processor in many forms, including, but not limited to information permanently stored on non-writable storage media, e.g., read only memory devices such as ROM or CD ROM discs readable by processors or computer I/O attachments; information stored on writable storage media, i.e. floppy discs and harddrives; or information convey to a computer/processor through communication media such as network and/or telephone networks via modems and/or internet or other interface devices. It should be understood that such media, when carrying processor readable instructions implementing the inventive concept represent alternate embodiments of the present invention.